Polymers derived from rosin and their methods of preparation

ABSTRACT

Methods of forming polymer material from rosin-derived material are provided. For example, a plurality of functionalized resin acids having a polymerizable functional group via controlled living polymerization can be polymerized into the polymeric material such that each polymer defines a functional end group and the polymeric material has a polydispersity index of about 1 to about 1.5. The resulting polymers are also described.

The present application claims priority to U.S. Provisional PatentApplication No. 61/278,553 titled “Preparation and Applications ofWell-Defined Polymers Derived from Rosin” filed on Oct. 8, 2009 by Tang,et al. and U.S. Provisional Patent Application No. 61/396,102 titled“Gum Rosin Containing Degradable Polymers” filed on May 21, 2010 byTang, et al., the disclosures of which are incorporated by referenceherein.

BACKGROUND

Synthetic plastics account for the use of 7% of fossil fuels in theworld. The limited resources and rising price of fossil fuels present achallenge to seek developing renewable resources for manufacturing of“green” plastics. However, applications of renewable polymers lagsignificantly behind petrochemical-derived polymers, partially becauseof limitations in the monomer resources and the derived polymers withcontrolled properties.

Rosin (including gum rosin, wood rosin and tall rosin) is an exudatefrom pine trees and other plants. The major components of rosin areresin acids: primarily abietic acid (AA) and levopimaric acid. Thepresence of a carboxyl group and/or conjugated double bonds in theirstructures imparts them tunable chemical reactivity: e.g. derivation ofa vinyl group. Rosin and its derivatives, produced millions of tonsannually, are generally used as ingredients for inks, vanishes,adhesives, paper size, cosmetics, medicines, chewing gums, etc. Some ofthem are used as additives or modifying agents for the improvement ofthe properties of synthetic polymers. However, the use of rosin asrenewable resources for the preparation of well-defined syntheticpolymers (e.g. homopolymers and block copolymers) has not yet beenexplored. The major reason behind this is that most rosin based polymersare prepared by step growth polymerization or free radicalpolymerization that lack controls on the polymer structures at molecularlevel, molecular weight, molecular weight distribution andfunctionality. The absence of the tunability of these parameters limitsthese polymers used for broader and promising alternatives to petroleumbased polymers such as thermoplastic resins, thermoplastic elastomers,polymeric varnishes, polymeric wax, adhesives, coatings, printing inksto shape memory polymers, polymer nanocomposites, pharmaceutics,anti-fouling materials, etc.

As such, a need exists for well-defined rosin-derived polymers withcontrollable molecular weight, low polydispersity and varied chemicaltopologies and chain functionality.

SUMMARY

Objects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In general, the present disclosure is directed toward methods of formingpolymer material from rosin-derived material. For example, a pluralityof functionalized resin acids having a polymerizable functional groupcan be polymerized via controlled and/or living polymerization. As such,the polymeric material can have well-controlled functional end groupsand can have a polydispersity index of about 1.0 to about 1.5. Theresulting polymers are also described.

Other features and aspects of the present invention are discussed ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof to one skilled in the art, is set forth moreparticularly in the remainder of the specification, which includesreference to the accompanying figures, in which:

FIG. 1 shows an example of well-defined rosin-derived polymers definingan ABA triblock copolymers for thermoplastic elastomers;

FIG. 2 shows an exemplary reaction of a hydroxyalkyl methacrylate and aresin acid(s) to form a functionalized resin acid(s);

FIG. 3 shows an example of rosin-substituted caprolactone homopolymersprepared by ring-opening polymerization and click reaction;

FIG. 4 shows an example of rosin-containing caprolactone diblockcopolymers prepared by ring-opening polymerization and atom transferradical polymerization; and

FIG. 5 shows an example of rosin-containing rosin-substitutedcaprolactone diblock copolymers prepared by ring-opening polymerization,atom transfer radical polymerization and click reaction.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present invention.

DEFINITIONS

As used herein, the term “polymer” generally includes, but is notlimited to, homopolymers; copolymers, such as, for example, block,graft, random and alternating copolymers; and terpolymers; and blendsand modifications thereof. Furthermore, unless otherwise specificallylimited, the term “polymer” shall include all possible geometricalconfigurations of the material. These configurations include, but arenot limited to isotactic, syndiotactic, and atatic symmetries.

The term “organic” is used herein to pertaining to a class of chemicalcompounds that are comprised of carbon atoms. For example, an “organicpolymer” is a polymer that includes carbon atoms in the polymerbackbone.

The “number average molecular weight” (M_(n)) is readily calculated byone of ordinary skill in the art, and generally refers to the ordinaryarithmetic mean or average of the molecular weights of the individualmacromolecules. It is determined by measuring the molecular weight of npolymer molecules, summing the weights, and dividing by n, such asrepresented in the formula:

${\overset{\_}{M}}_{n} = \frac{\sum\limits_{i}{N_{i}M_{i}}}{\sum\limits_{i}N_{i}}$where N_(i) is the number of molecules of molecular weight M_(i). Thenumber average molecular weight of a polymer can be determined by gelpermeation chromatography and all colligative methods, like vaporpressure osmometry or end-group determination.

The “weight average molecular weight” (M_(w)) is readily calculated byone of ordinary skill in the art, and generally refers to:

${\overset{\_}{M}}_{w} = \frac{\sum\limits_{i}{N_{i}M_{i}^{2}}}{\sum\limits_{i}{N_{i}M_{i}}}$where N_(i) is the number of molecules of molecular weight M_(i). Theweight average molecular weight can be determined by gel permeationchromatography, light scattering, small angle neutron scattering (SANS)and X-ray scattering.

The polydispersity index (PDI) is a measure of the distribution ofmolecular mass in a given polymer sample. The PDI calculated is theweight average molecular weight divided by the number average molecularweight (i.e., PDI=M_(w)/M_(n)). It indicates the distribution ofindividual molecular masses in a batch of polymers. The PDI has a valueequal to or greater than 1, but as the polymer chains approach uniformchain length, the PDI approaches unity (i.e., 1).

DETAILED DESCRIPTION

Reference now will be made to the embodiments of the invention, one ormore examples of which are set forth below. Each example is provided byway of an explanation of the invention, not as a limitation of theinvention. In fact, it will be apparent to those skilled in the art thatvarious modifications and variations can be made in the inventionwithout departing from the scope or spirit of the invention. Forinstance, features illustrated or described as one embodiment can beused on another embodiment to yield still a further embodiment. Thus, itis intended that the present invention covers such modifications andvariations as come within the scope of the appended claims and theirequivalents. It is to be understood by one of ordinary skill in the artthat the present discussion is a description of exemplary embodimentsonly, and is not intended as limiting the broader aspects of the presentinvention, which broader aspects are embodied exemplary constructions.

Generally speaking, the present disclosure is directed to well-definedrosin-derived polymers and their methods of production. Thus, asynergistic strategy has been developed to form well-defined polymersfrom a renewable resource—rosin, which is an exudate from pine trees andother plants. Accordingly, well-defined rosin-derived polymers withcontrolled molecular weight, low polydispersity, chemical topologies andend group functionality can be developed to provide tailored propertiesfor applications in the areas of thermoplastic resins, thermoplasticelastomers, adhesives, printing inks, paper-sizing, varnishes, coatings,nanocomposites, shape memory materials, anti-fouling materials,nanoporous membranes, etc.

The presently disclosed methods can allow for controllable molecularweight, low polydispersity and varied chemical topologies and chainfunctionality of the polymers. Thus, a broad strategy is generallydisclosed allowing for the development of well-defined polymers derivedfrom renewable resources, which can provide access to diverse polymersthat rosin offers, but with controlled structures and molecular weight.Successful implementation of these rosin-based polymers can lead toreplacement of petrochemical-based polymers, thus reducing consumptionof major synthetic polymers from fossil fuels.

More particularly, methods are provided for preparing well-definedpolymers from rosin based materials (e.g., rosin based monomers, such asmodified resin acids). The well-defined polymers can include blockcopolymers, random copolymers, graft copolymers, star copolymer, ororganic/inorganic hybrids that contain at least one polymerized monomerderived from rosin. Such well-defined polymers have controllablecompositions, controllable molecular weight, a narrow molecular weightdistribution, and end group functionality.

Rosin-derived polymers developed according to the present disclosure canhave applications ranging from thermoplastic resins, thermoplasticelastomers, varnishes, wax, paper sizing, adhesives, coatings, printinginks to shape memory polymers, nanocomposites, pharmaceutics,anti-fouling, nanoporous membrane, etc.

Generally, the polymers can be formed by direct polymerization ofrosin-derived monomers or by attaching rosin based materials to existingpolymer substrates. For example, rosin based materials (e.g., resinacids) can be functionalized to form rosin-derived monomers and thenpolymerized, as discussed in greater detail below.

I. Rosin-Derived Monomers

Rosin's major components include resin acids, which can be obtained frompine trees and other plants, in a number of isomeric forms. Generally,the resin acids have a three ring structure (e.g., ahydrophenanthrene-based three ring structure) with a carboxylic acidfunctional group (i.e., —COOH). Prevalent resin acids include, but arenot limited to, abietic acid, neoabietic acid, dehydroabietic acid,palustric acid, levopimaric acid, pimaric acid, isopimaric acids, etc.Nearly all resin acids have the same basic skeleton of a 3-ring fusedsystem with the empirical formula C₁₉H₂₉COOH.

Six particularly suitable resin acids for use as monomers in thepresently disclosed methods and polymers include levopimaric acid,abietic acid, dehydroabietic acid, hydroabietic acid, pimaric acid,isopimaric acid, and mixtures thereof due to their availabilitycommercially at various purities. The chemical structures of each ofthese resin acids are provided below and are generally known in the art:

As shown, each of these resin acids have a carboxylic acid group (i.e.,R—COOH) attached to the hydrophenathrene-based rings.

The resin acid or mixture of resin acids (collectively referred to as“resin acid(s)”) can be purified through standard techniques to providea substantially pure resin acid(s) starting material for the polymers.For example, the resin acid or mixture of resin acids can be purified toat least about 95% by weight, such as at least about 98% by weight.

In particular embodiments, the resin acid or mixture of resin acids canbe purified to be about 99% by weight to substantially free from othermaterials. As used herein, the term “substantially free” means no morethan an insignificant trace amount present and encompasses completelyfree (e.g., 0% by weight up to about 0.0001% by weight). Thus, most orsubstantially all of the other organic material in the rosin can beseparated from the resin acid(s) prior to functionalization.

In alternative embodiments, the resin acid(s) can be utilizedcollectively in their natural rosin form.

II. Functionalized Rosin-Derived Monomers

According to the present method of forming the well-defined polymers,the resin acid(s) can be functionalized with polymerizable groups, suchas vinyl groups (e.g., an acrylate group, a methacrylate group, etc.) orstrained ring functional groups (e.g., cyclic ester groups likecaprolactone or lactide, a norbornene group, a cyclopentene group,etc.). Specifically, the carboxylic acid groups attached from thehydrophenanthrene-based rings can be functionalized into thepolymerizable groups.

For example, the carboxylic acid groups on the resin acid(s) can bereacted with an alcohol (R′—OH) to form a carboxylic ester (R—COO—R′) byconverting resin acid(s) to acid halides followed by simpleesterification reaction using triethylamine as the base.

In one particular embodiment, the alcohol can be an hydroxyalkylacrylate or a hydroxyalkyl methacrylate (collectively referred to as“hydroxyalkyl(meth)acrylate”). Suitable examples of such hydroxyalkylmethacrylates can include hydroxymethyl methacrylate, hydroxyethylmethacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, andso forth.

Upon this reaction, the functionalized resin acid(s) will have vinylfunctional group in place of the carboxylic acid function group of theresin acid(s) that is readily polymerizable (e.g., an acrylate ormethacrylate functional group).

For example, FIG. 2 shows an exemplary reaction of a hydroxyalkylmethacrylate and a resin acid(s) to form a resin acid(s)-derivedmethacrylate as the functionalized resin acid(s). In FIG. 2, Rrepresents any of the resin acids, and n is an integer representing thenumber of carbons (i.e., —CH₂—) in the chain (e.g., 1 to 10, such as 2to 5).

III. Polymerization

The functionalized resin acid(s) can be subjected to controlledpolymerizations, such as controlled living polymerizations (CLPs) orcontrolled ring-opening polymerizations. Through the use of thesecontrolled polymerizations, polymers can be produced with lowpolydispersity, high functionality (e.g., a terminal functional group),and diverse architectures. Thus, these methods are ideal for blockpolymer and/or graft polymer synthesis.

Controlled living polymerization generally refers to chain growthpolymerization which proceeds with significantly suppressed terminationor chain transfer steps. Thus, polymerization in CLP proceeds until allmonomer units have been consumed, and the addition of monomer results incontinued polymerization, making CLP ideal for block polymer and graftpolymer synthesis. The molecular weight of the resulting polymer isgenerally a linear function of conversion so that the polymeric chainsare initiated and grow substantially uniformly. Thus, CLPs provideprecise control on molecular structures, functionality and compositions.Thus, these polymers can be tuned with desirable compositions andarchitectures.

Controlled living polymerizations can be used to produce blockcopolymers because CLP can leave a functional terminal group on thepolymer formed (e.g., a halogen functional group). For example, in thecopolymerization of two monomers (A and B) allowing A to polymerize viaCLP will exhaust the monomer in solution with minimal termination. Aftermonomer A is fully reacted, the addition of monomer B will result in ablock copolymer.

Controlled ring-opening polymerizations can utilize suitable catalystssuch as tin(II) to open the rings of monomers to form a polymer.

The functionalized resin acid(s) can be polymerized alone (e.g., as asingle resin acid or a combination of multiple resin acids) or withother monomers (e.g., styrene, methacrylate, acrylate, lactide,caprolactone, etc., or combinations thereof). As such, in specificembodiments, block copolymers, random copolymers, graft copolymers, starcopolymer or organic/inorganic hybrids can each bear other monomer unitsselected from olefins, conjugated dienes, methacrylates, styrenes,acrylates, acrylamides, and acrylonitriles, esters, ethers, urethanes,ureas, amides and other functional monomer units thereof.

Specific polymerization techniques can be utilized to form thewell-defined polymers, as discussed in greater detail below.

A. Atom Transfer Radical Polymerization

Atom transfer radical polymerization (ATRP) is an example of a livingradical polymerization. The control is achieved through anactivation-deactivation process, in which most of the reaction speciesare in dormant format, thus significantly reducing chain terminationreaction. The four major components of ATRP include the monomer,initiator, ligand, and catalyst. ATRP is particularly useful where thefunctionalized resin acid(s) have a vinyl functional group (e.g., a(meth)acrylate group).

Organic halides are particularly suitable initiators, such as alkylhalides (e.g., alkyl bromides, alkyl chlorides, etc.). For instance, inone particular embodiment, the alkyl halide can be ethyl2-bromoisobutyrate. The shape or structure of the initiator can alsodetermine the architecture of the resulting polymer. For example,initiators with multiple alkyl halide groups on a single core can leadto a star-like polymer shape, such as shown in FIG. 1.

The catalyst can determine the equilibrium constant between the activeand dormant species during polymerization, leading to control of thepolymerization rate and the equilibrium constant. In one particularembodiment, the catalyst is a metal having two accessible oxidationstates that are separated by one electron, and a reasonable affinity forhalogens. One particularly suitable metal catalyst for ATRP is copper(I).

The ligands can be linear amines or pyridine-based amines.

Depending on the target molecular weight of final polymers, the monomerto initiator ratios can range from less than about 10 to more than about1,000 (e.g., about 10 to about 1,000). Other reaction parameters can bevaried to control the molecular weight of the final polymers, such assolvent selection, reaction temperature, and reaction time. Forinstance, solvents can include conventional organic solvents such astetrahydrofuran, toluene, dimethylformamide, anisole, acetonitrile,dichloromethane, etc. The reaction temperature can range from roomtemperature (e.g., about 20° C.) to about 120° C. The reaction time canbe from less than about 1 h to about 48 h.

B. Reversible Addition-Fragmentation Chain Transfer Polymerization

Reversible Addition-Fragmentation chain Transfer polymerization (RAFT)is another type of controlled radical polymerization. RAFTpolymerization uses thiocarbonylthio compounds, such as dithioesters,dithiocarbamates, trithiocarbonates, and xanthates, in order to mediatethe polymerization via a reversible chain-transfer process. RAFTpolymerization can be performed by simply adding a chosen quantity ofappropriate RAFT agents (thiocarbonylthio compounds) to a conventionalfree radical polymerization. RAFT polymerization is particularly usefulwhere the functionalized resin acid(s) have a vinyl functional group(e.g., a (meth)acrylate group).

Typically, a RAFT polymerization system includes the monomer, aninitiator, and a RAFT agent (also referred to as a chain transferagent). Because of the low concentration of the RAFT agent in thesystem, the concentration of the initiator is usually lower than inconventional radical polymerization. Suitable radical initiators can beazobisisobutyronitrile (AlBN), 4,4′-azobis(4-cyanovaleric acid) (ACVA),etc.

RAFT agents are generally thiocarbonylthio compounds, such as generallyshown below:

where the z group primarily stabilizes radical species added to the C═Sbond and the R group is a good homolytic leaving group which is able toinitiate monomers. For example, the z group can be an aryl group (e.g.,phenyl group, benzyl group, etc.), an alkyl group, etc. The R″ group canbe an organic chain terminating with a carboxylic acid group.

As stated, RAFT is a type of living polymerization involving aconventional radical polymerization in the presence of a reversiblechain transfer reagent. Like other living radical polymerizations, thereis minimized termination step in the RAFT process. The reaction isstarted by radical initiators (e.g., AIBN). In this initiation step, theinitiator reacts with a monomer unit to create a radical species whichstarts an active polymerizing chain. Then, the active chain reacts withthe thiocarbonylthio compound, which kicks out the homolytic leavinggroup (R″). This is a reversible step, with an intermediate speciescapable of losing either the leaving group (R″) or the active species.The leaving group radical then reacts with another monomer species,starting another active polymer chain. This active chain is then able togo through the addition-fragmentation or equilibration steps. Theequilibration keeps the majority of the active propagating species intothe dormant thiocarbonyl compound, limiting the possibility of chaintermination. Thus, active polymer chains are in an equilibrium betweenthe active and dormant species. While one polymer chain is in thedormant stage (bound to the thiocarbonyl compound), the other is activein polymerization.

By controlling the concentration of initiator and thiocarbonylthiocompound, the molecular weight of the polymers can be controlled withlow polydispersities.

Depending on the target molecular weight of final polymers, the monomerto RAFT agent ratios can range from about less than about 10 to morethan about 1000 (e.g., about 10 to about 1,000). Other reactionparameters can be varied to control the molecular weight of the finalpolymers, such as solvent selection, reaction temperature, and reactiontime. For instance, solvents can include conventional organic solventssuch as tetrahydrofuran, toluene, dimethylformamide, anisole,acetonitrile, dichloromethane, etc. The reaction temperature can rangefrom room temperature (e.g., about 20° C.) to about 120° C. The reactiontime can be from less than about 1 h to about 48 h.

The RAFT process allows the synthesis of polymers with specificmacromolecular architectures such as block, gradient, statistical,comb/brush, star, hyperbranched, and network copolymers.

Because RAFT polymerization is a form of living radical polymerization,it is ideal for synthesis of block copolymers. For example, in thecopolymerization of two monomers (A and B) allowing A to polymerize viaRAFT will exhaust the monomer in solution with significantly suppressedtermination. After monomer A is fully reacted, the addition of monomer Bwill result in a block copolymer. One requirement for maintaining anarrow polydispersity in this type of copolymer is to have a chaintransfer agent with a high transfer constant to the subsequent monomer(monomer B in the example).

Using a multifunctional RAFT agent can result in the formation of a starcopolymer. RAFT differs from other forms of CLPs because the core of thecopolymer can be introduced by functionalization of either the R groupor the Z group. While utilizing the R group results in similarstructures found using ATRP or NMP, the use of the Z group makes RAFTunique. When the Z group is used, the reactive polymeric arms aredetached from the core while they grow and react back into the core forthe chain-transfer reaction.

C. Nitroxide-Mediated Polymerization

Nitroxide-mediated polymerization (NMP) is another form of controlledliving polymerization utilizing a nitroxide radical, such as shownbelow:

where R1 and R2 are, independently, organic groups (e.g., aryl groupssuch as phenyl groups, benzyl groups, etc.; alkyl groups, etc.). NMP isparticularly useful where the functionalized resin acid(s) have a vinylfunctional group (e.g., a (meth)acrylate group).

D. Ring-Opening Metathesis Polymerization

Ring-opening metathesis polymerization (ROMP) is a type of olefinmetathesis polymerization. The driving force of the reaction is reliefof ring strain in cyclic olefins (e.g. norbornene or cyclopentene) inthe presence of a catalyst. The catalysts used in a ROMP reaction caninclude a wide variety of metals and range from a simple RuCl₃/alcoholmixture to Grubbs' catalyst.

In this embodiment, the functionalized resin acid can include a strainedring functional group, such as a norbornene functional group, acyclopentene functional group, etc. to form the rosin derived polymers.For example, norbornene is a bridged cyclic hydrocarbon that has acyclohexene ring bridged with a methylene group in the para position.

The ROMP catalytic cycle generally requires a strained cyclic structurebecause the driving force of the reaction is relief of ring strain.After formation of the metal-carbene species, the carbene attacks thedouble bond in the ring structure forming a highly strainedmetallacyclobutane intermediate. The ring then opens giving thebeginning of the polymer: a linear chain double bonded to the metal witha terminal double bond as well. The new carbene reacts with the doublebond on the next monomer, thus propagating the reaction.

E. Ring-Opening Polymerization

In one particular embodiment, where the functionalized resin acidincludes a strained ring function group (e.g., a caprolactone orlactide), ring-opening polymerization (ROP) may be used to form therosin derived polymers. For example, a rosin-substituted caprolactone isa polymerizable ester, which can undergo polymerization with the aid ofan alcohol as an initiator and a tin-based reagent as a catalyst.

IV. Rosin-Derived Polymers and Block Co-Polymers

Through CLP, the resulting polymeric material can include well-definedpolymers, referencing the substantially low polydispersity index. Forexample, the resulting polymers can have a PDI of less than 1.5, such asabout 1.05 to about 1.45.

The molecular weight of these resulting polymers can be controlled asdesired. In most embodiments, the molecular weight of the resultingpolymers can be about 2,000 g/mol to about 1,000,000 g/mole, such asabout 10,000 g/mol to about 750,000 g/mole. However, in otherembodiments, the molecular weight can be larger or smaller.

Generally, the composition of rosin-derived units (i.e., thefunctionalized resin acid(s) monomers) is primarily in the range ofabout 10% by weight to about 95% by weight (e.g., about 50% by weight toabout 80% by weight). In one particular embodiment, the resultingpolymer includes only functionalized resin acid(s) monomers (i.e., about100% functionalized resin acid(s) monomers).

However, in alternative embodiments, these resulting polymers can bearother comonomers. Particularly suitable comonomers can include thosewith polymerizable functional groups (e.g., vinyl functionality), suchas styrene, methacrylate, acrylate, lactide, caprolactone, etc, andcombinations thereof.

In one particular embodiment, the functionalized resin acid(s) monomerscan be used for preparation of block copolymers with two monomers (ABdiblock copolymer or ABA triblock copolymers) or three monomers (ABCtriblock copolymers).

In an alternative embodiment, the functionalized resin acid(s) monomerscan be used for preparation of graft copolymers, such as (i) from apolymer backbone; (ii) from a curve surface such as silicananoparticles; (iii) from a flat surface such as silicon wafersubstrates, or the like.

Additionally, the functionalized resin acid(s) monomers can be used forpreparation of star copolymers, for organic and/or inorganicnanocomposites, etc.

Rosin-derived block copolymers exhibit microphase separation, which cancombine multifunctional properties from the constituent components. Theproperties can be tuned by changing the molecular weight, compositionsand chemical structures of each segment.

In one particular embodiment, degradable polymers can be synthesizedfrom rosin based materials. Such degradable polymers can have manyapplications including packaging materials, auto parts, drug delivery,tissue engineering, membrane, gas storage, etc. Additionally, theintegration of rosin with degradable polymers can have severalbenefits: 1) more environmentally friendly, through the template ofdegradable polymers, degradation would produce residual rosin or rosinpolymers, which have much lower molecular weight (therefore morecompatible with environments) than those rosin polymers withoutdegradation templates; 2) increased renewable capacity for non-renewabledegradable polymers by increasing the volume of rosin in the degradablepolymers; and 3) new thermal, mechanical and degradability propertiesoriginating from rosin moiety.

In particular, the functionalized resin acid(s) can be co-polymerizedwith degradable comonomers. As such, the resulting copolymers caninclude the rosin-derived units in about 10% by weight to about 90% byweight, while the degradable comonomers are present in about 10% byweight to about 90% by weight. Suitable degradable comonomers caninclude caprolactone, lactide, glycolic acid, hydroxyalkanoic acids,hydroxybutyric acid, hydroxyvaleric acid, trimethylene carbonate, etc.,or combinations thereof. The comonomer can be used to form randomcopolymers, block copolymers, graft copolymers, etc.

For example, poly(2-chloro-ε-caprolactone) homopolymers can be preparedthrough ring-opening polymerization, and then converted intopoly(2-azide-ε-caprolactone) homopolymers, which click with alkynecontaining dehydroabietic moiety. Polycaprolactone is degraded underacidic conditions or bio conditions. The caprolactone unit can bereplaced by other degradable units, e.g. lactide, glycolic acid,hydroxyalkanoic acids, hydroxybutyric acid, hydroxyvaleric acid, andtrimethylene carbonate. The molecular weight of these polymers can be inthe range of about 2,000 g/mol to about 1,000,000 g/mole.

FIG. 3 illustrates a scheme for one particular embodiment, wherehomopolymers of caprolactone with a dehydroabietic moiety are used asthe side groups in the preparation of the polymer.

FIG. 4 illustrates a scheme for another particular embodiment, wherediblock copolymers of caprolactone and dehydroabietic ethyl acrylate canbe prepared. Specifically, polycaprolactone and poly(dehydroabieticethyl acrylate) block copolymers were prepared through ring-openingpolymerization and atom transfer radical polymerization, respectively.

FIG. 5 illustrates a scheme for another particular embodiment, wherediblock copolymers of dehydroabietic-substituted caprolactone anddehydroabietic ethyl acrylate can be prepared. As shown,poly(2-chloro-ε-caprolactone) and poly(dehydroabietic ethyl acrylate)block copolymers can be prepared through ring-opening polymerization andatom transfer radical polymerization respectively.Poly(2-chloro-ε-caprolactone) segments can then be converted intopoly(2-azide-ε-caprolactone), which click with alkyne containingdehydroabietic moiety.

EXAMPLES Example 1

Rosin-derived ABA triblock copolymers were prepared for the use asthermoplastic elastomers using atom transfer radical polymerization.Rosin-derived polymers accounted for both inner and outer blocks (i.e.,the “A” blocks). The synthesis fully utilized rosin based materials asrenewable resources by taking advantage of tunable properties of rosin(e.g. different glass transition temperature T_(g)). Specifically,poly(dehydroabietic acrylate)-block-poly(hydroabietic butylacrylate)-block-Poly(dehydroabietic acrylate) was prepared. FIG. 1illustrates this ABA triblock copolymer, which exhibits strong phaseseparation with component A forming the hard phase (serving as aphysical cross-linker) dispersed in the continuous soft rubbery matrixof component B. As shown, component A is a block of dehydroabietic acidfunctionalized with an acrylate group that has been polymerized andcomponent B is a block of poly(hydroabietic butyl acrylate).

The soft and hard blocks inside and outside respectively, were preparedby sequential polymerization. Difunctional poly(hydroabietic butylacrylate) macroinitiators were synthesized using dimethyl2,6-dibromoheptanedioate as initiators, copper (I)bromide/Pentamethyldiethylenetriamine as ligands. The ABA triblockcopolymers were prepared by chain extension of difunctionalpoly(hydroabietic butyl acrylate) macroinitiators withpoly(dehydroabietic acrylate) in the presence of copper (I) bromide andpentamethyldiethylenetriamine.

The synthesis of ABA triblock copolymers can be carried out using othercontrolled polymerizations e.g. group transfer polymerization,nitroxide-mediated polymerization, reversible addition fragmentationtransfer polymerization. One of blocks in the ABA triblock copolymerscan be other types of polymerizable monomers, such as styrene,methacrylate, acrylate, lactide, caprolactone. All these ABA triblockcopolymers exhibit strong phase separation derived from mechanicallydifferent domains of rigid and soft segments

Example 2

Rosin based ABA triblock copolymers were prepared with rigidpoly(dehydroabietic acrylate) as the outer segment, through thesynthesis of difunctional poly(3-hydroxybutyrate) (PHB) by aring-opening polymerization of butyrolactone in the presence of1,4-butanediol with distannoxane as the catalyst. PHB was used as theinner block due to its biocompatibility and softness (i.e., T_(g)=−2±3°C.). The hydroxyl-terminated PHB was further reacted withbromoisobutyrate bromide to form an atom transfer radical polymerizationmacroinitiator, which was then chain extended with dehydroabieticacrylate using copper (I) bromide and tris[2-(dimethylamino)ethyl]amineas catalyst/ligands under 80° C. for 16 hours, yielding ABA triblockcopolymers.

Example 3

Rosin-derived acrylic block copolymers were prepared for the use aspigment dispersants using group transfer polymerization. A 25 ml schlenkflask was purged with nitrogen gas. This flask was charged with 0.42 gdimethylketene methyl trimethylsilyl acetal, 0.05 ml xylene and 0.02 mLof a 1M solution of tetrabutylammonium m-chlorobenzoate in acetonitrile.The reaction mixture was then cooled to 7° C. Glycidyl methacrylate (3.4g) was added in 5 min. The temperature rose to 45° C. After 60 min,dehydroabietic methacylate (10.2 g) was added. The reaction mixture washeated at 65° C. After another 60 min, methanol was added and flask wascooled to room temperature. The synthesis of ABA triblock copolymers canbe carried out using other controlled polymerizations e.g. atom transferradical polymerization, nitroxide-mediated polymerization, reversibleaddition fragmentation transfer polymerization.

Example 4

Rosin-derived acrylic polymers/silica nanoparticle nanocomposites wereprepared. The main principle is to use “grafting from” route to graftrosin-derived polymers from nanoparticle surface. Silica nanoparticles(size about 20 nm) were functionalized with atom transfer radicalpolymerization initiator by reacting 1-(chlorodimethylsilyl)propyl2-bromoisobutyrate with the hydroxyl groups on the silica particlesurface. These functionalized silica nanoparticles, CuBr, anddi-4,4′-(5-nonyl)-2,2′-bipyridine were mixed in a 50 mL Schlenk flask.The mixture was treated three time freeze-pump-thaw cycles, and thenabietic acrylate (already purged with nitrogen) was added to the flask.The reaction mixture was placed in an 80° C. oil bath for 24 hours.These nanoparticles can be extended to other types of materials such asgold nanoparticles and quantum dots.

Example 5

Rosin-containing caprolactone-based homopolymers (as shown in FIG. 3)were prepared. The synthesis integrated rosin components into degradablemonomers as substituted groups. A typical procedure for the synthesis isdescribed as follows: 2-chloro-ε-caprolactone and benzyl alcohol, andtoluene were placed in a Schlenk flask, a solution of tin(II)2-ethylhexanoate (Sn(EH)₂) was added and the flask was purged with N₂.The mixture was stirred at 120° C. for 12 h to yieldpoly(2-chloro-ε-caprolactone) homopolymers. Thepoly(2-chloro-ε-caprolactone) was stirred with sodium azide indimethylformamide for 24 h, yielding poly(2-azide-ε-caprolactone). Clickreaction between poly(2-azide-ε-caprolactone) and dehydroabietic alkyneresulted in polycaprolactone with dehydroabietic as substituted group.

Example 6

Polycaprolactone-b-poly(dehydroabietic ethyl acrylate) diblockcopolymers were prepared, as shown in FIG. 4, involving the synthesis ofpolycaprolactone by a ring-opening polymerization andpoly(dehydroabietic ethyl acrylate) by atom transfer radicalpolymerization. An initiator containing both functional groups for ROPand ATRP was used. A typical procedure for the synthesis is described asfollows: caprolactone and 2-hydroxylethyl bromoisobutyrate, and toluenewere placed in a Schlenk flask, a solution of Sn(EH)₂ was added and theflask was purged with N₂. The mixture was stirred at 120° C. for 12 h toyield polycaprolactone homopolymers. The polycaprolactone was mixed withdehydroabietic ethyl acrylate, tris[2-(dimethylamino)ethyl]amine intetrahydrofuran and purged with N₂. Copper (I) bromide was then added tothe mixture under nitrogen purge. The mixture was then stirred at 90° C.for 16 h, yielding the desired block copolymers.

Example 7

Polycaprolactone-b-poly(dehydroabietic ethyl acrylate) diblockcopolymers with caprolactone substituted with dehydroabietic group wereprepared, as shown in FIG. 5. The synthesis combines examples 5 and 6.First, diblock copolymerspoly(2-chloro-ε-caprolactone-b-poly(dehydroabietic ethyl acrylate) wereprepared using the procedure described in example 6. The substitutedchloro group was then converted into dehydroabietic group, using theprocedure described in example 5.

Example 8

Rosin-containing lactide-based homopolymers were prepared using aprocedure similar to example 5. Propargyl glycolide, Sn(EH)₂ and4-Pert-butylbenzyl alcohol solutions were mixed in a Schlenk flask andpurged with N₂. After removing solvent under reduced pressure, themixture was stirred at 130° C. for 12 h, yielding alkyne-substitutedpolylactide. Click reaction between alkyne-substituted polylactide anddehydroabietic azide resulted in dehydroabietic-substituted polylactide.

Example 9

Polylactide-b-poly(dehydroabietic ethyl acrylate) diblock copolymerswere prepared using a procedure similar to example 6, involving thesynthesis of polylactide by a ring-opening polymerization andpoly(dehydroabietic ethyl acrylate) by atom transfer radicalpolymerization. An initiator containing both functional groups for ROPand ATRP was used. A typical procedure for the synthesis is described asfollows: lactide and 2-hydroxylethyl bromoisobutyrate, and toluene wereplaced in a Schlenk flask, a solution of Sn(EH)₂ was added and the flaskwas purged with N₂. The mixture was stirred at 130° C. for 12 h to yieldpolylactide homopolymers. The polylactide was mixed with dehydroabieticethyl acrylate, tris[2-(dimethylamino)ethyl]amine (Me6Tren) intetrahydrofuran and purged with N₂. Copper (I) bromide was then added tothe mixture under nitrogen purge. The mixture was then stirred at 90° C.for 16 h, yielding the desired block copolymers.

Example 10

Polylactide-b-poly(dehydroabietic ethyl acrylate) diblock copolymerswith lactide substituted with dehydroabietic group were prepared. Thesynthesis combines examples 8 and 9. First, diblock copolymerspoly(propargyl glycolide)-b-poly(dehydroabietic ethyl acrylate) wereprepared using the procedure described in example 9. The substitutedgroup was then converted into dehydroabietic group, using the proceduredescribed in example 8.

These and other modifications and variations to the present inventionmay be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present invention, which ismore particularly set forth in the appended claims. In addition, itshould be understood the aspects of the various embodiments may beinterchanged both in whole or in part. Furthermore, those of ordinaryskill in the art will appreciate that the foregoing description is byway of example only, and is not intended to limit the invention sofurther described in the appended claims.

What is claimed:
 1. A method of forming polymer material fromrosin-derived material, the method comprising: polymerizing a pluralityof functionalized resin acids having a polymerizable functional groupvia controlled polymerization into the polymeric material, wherein eachpolymer defines a functional end group, and wherein the polymericmaterial has a polydispersity index of about 1 to about 1.5.
 2. Themethod of claim 1, wherein the polymer has a polydispersity index ofabout 1.05 to about 1.45.
 3. The method of claim 1, wherein the polymerhas a polydispersity index of about 1.5.
 4. The method of claim 1,wherein the polymerizable functional group comprises a vinyl group. 5.The method of claim 4, wherein the functional end group comprises avinyl group.
 6. The method of claim 4, further comprising: reacting acarboxylic acid group on a resin acid with an amine to form thefunctionalized resin acid having a vinyl functional group.
 7. The methodof claim 4, further comprising: reacting a carboxylic acid group on aresin acid with an alcohol to form the functionalized resin acid havinga vinyl functional group.
 8. The method of claim 7, wherein the alcoholcomprises a hydroxyalkyl (meth)acrylate.
 9. The method of claim 7,wherein the alcohol comprises a hydroxyalkyl methacrylate.
 10. Themethod of claim 4, wherein the plurality of functionalized resin acidsare polymerized via controlled living polymerization.
 11. The method ofclaim 10, wherein the controlled living polymerization comprises atomtransfer radical polymerization, wherein the functionalized resin acidis polymerized in a polymerization solution comprising thefunctionalized resin acid, an initiator, a ligand, and a catalyst. 12.The method of claim 11, wherein the initiator comprises an organichalide.
 13. The method of claim 12, wherein the organic halide comprisesan alkyl halide.
 14. The method of claim 11, wherein the catalystcomprises copper(I).
 15. The method of claim 10, wherein the controlledliving polymerization comprises reversible addition-fragmentation chaintransfer polymerization, wherein the functionalized resin acid ispolymerized in a polymerization solution comprising the functionalizedresin acid, an initiator, and a chain transfer agent.
 16. The method ofclaim 15, wherein the initiator comprises azobisisobutyronitrile,4,4′-azobis(4-cyanovaleric acid), or combinations thereof.
 17. Themethod of claim 15, wherein the chain transfer agent comprises athiocarbonylthio compound.
 18. The method of claim 17, wherein the chaintransfer agent comprises

where z represents an aryl group or an alkyl group and R″ represents anorganic chain terminating with a carboxylic acid group.
 19. The methodof claim 10, wherein the controlled living polymerization comprisesnitroxide-mediated polymerization, wherein the functionalized resin acidis polymerized in a polymerization solution comprising thefunctionalized resin acid and a nitroxide radical.
 20. The method ofclaim 19, wherein the nitroxide radical comprises

where R1 and R2 are, independently, organic groups.
 21. The method ofclaim 1, wherein the polymerizable functional group comprises a strainedring functional group.
 22. The method of claim 21, wherein the pluralityof functionalized resin acids are polymerized via controlledring-opening polymerization.
 23. The method of claim 22, wherein thecontrolled ring-opening polymerization comprises ring-opening metathesispolymerization, and wherein the strained ring functional group comprisesa cyclic olefin functional group.
 24. The method of claim 23, whereinthe cyclic olefin functional group comprises a norbornene functionalgroup or a cyclopentene functional group.
 25. The method of claim 23,wherein the cyclic olefin functional group comprises a cyclic estergroup.
 26. The method of claim 25, wherein the cyclic ester groupcomprises caprolactone or lactide.
 27. The method of claim 1, whereinthe functionalized resin acid comprises a resin acid, wherein the resinacid is abietic acid, neoabietic acid, dehydroabietic acid, palustricacid, levopimaric acid, pimaric acid, isopimaric acids, or combinationsthereof.
 28. The method of claim 1, wherein the polymer has a molecularweight of about 2,000 g/mol to about 1,000,000 g/mole.
 29. The method ofclaim 1, wherein the polymer has a molecular weight of about 10,000g/mol to about 750,000 g/mole.
 30. The method of claim 1, wherein thefunctionalized resin acid is copolymerized with a comonomer.
 31. Themethod of claim 30, wherein the comonomer is a degradable comonomer. 32.The method of claim 31, wherein the degradable comonomer comprisescaprolactone, lactide, glycolic acid, hydroxyalkanoic acids,hydroxybutyric acid, hydroxyvaleric acid, trimethylene carbonate, orcombinations thereof.
 33. The method of claim 1, further comprising:allowing polymerization to exhaust substantially all availablefunctionalized resin acids to form a first block; polymerizing aplurality of comonomers to form a second block attached to the firstblock.
 34. The method of claim 33, further comprising: allowingpolymerization to exhaust substantially all available comonomers to formthe second block; and polymerizing a plurality of functionalized resinacids to form a third block attached to the second block.